Mechanism for precision switches



Sept. 30, 1947. MlLLER 2,428,172

MECHANISM FOR PRECISION SWITCHES Filed March 16, 1945 IL .5: I

HQ EDWIN AUGUST MILLER W Patented Sept. 30, 1947 UNITED srAres PATENTOFFICE Claims. 1

This invention relates to mechanism for precision switches, includingswitches adapted for alternate electric circuits.

The objects of the invention are to provide a snap action switch whichmaintains a constant maximum contact pressure up to the breaking point;to provide a switch having an actuating means including a flat springmaterial to which resilient properties are imparted while a portion ofthe material is held in a predetermined manner; and to provide a switchthe mechanism of which is compact, with the least required exertivepressure of operation, and adapted for a reduced arc of oscillation.

Referring to the accompanying drawing, the

' Figure 1 is an erect elevation of the device, illustrating itsinsulation casing in cross-section and its mechanism in a maintainedat-rest position; Figure 2 is a similar elevation but illustrating itsmechanism in an operated position; Figure 3 is a top surface view of theoscillating member; Figure 4 is a perspective view of the link member;Figure 5- is a perspective view of the leaf spring member; and theFigures 6 and 7 are diagrammatic layouts of two mechanical positions ofthe oscillating member and associated parts.

With more particular reference to the accompanying drawing, there isillustrated one form only of the invention with regard to the novelmechanism and manner by which the improvement herein set forth isachieved. Other forms within the scope of the invention may be obvious.

The casing I, of insulation material, illustrated I in cross-section,accessibly provides wire connection terminals 2, 3 and 4 adapted forelectric wiring (not illustrated) for the establishment of separatealternate circuits within which the switch may be inserted. The innerextremities of terminals 2 and 3 provide the spacedly aligned fixedcontacts 5 and 6 rigid with said casing I.

v The sheet-metal oscillating body member I, one

end of which is anchored, as at 8, within the casing I where it isprovided with a permanent connection with the inner end of the terminal4, as illustrated by the Figures 1 and 2, carries at its opposite endthe upper and lower superposed contact surfaces 9 and I0, respectively,adapted for alternate engagements with the fixed contacts 5 and 6 inmaintained at-rest and operated positions of the oscillating body memberI. The tongue II is illustrated-as integral with the body member 1 andpendulously formed by being cut on three sides from within the centralsurfacelength thereof, the extremity of the tongue II being shortened,as at IIB, leaving unoccupied a portion of the tongue operating space1A. The

tongue I however, is extended by means of the link I2 of which one endedge is turned downwardly, as at I3, and at the opposite end edge isprovided with the extended lugs I3A, the

turned portion I3 being provided at its side edges with open marginalrecesses I4 into which fit the tree lower end is movably held within theslot I6 of the casing I. Said leaf spring I5 is provided at its sideedges with the open recess II within which fit the extended lugs I3A ofthe link I2 as a means of hinged assembly. The tension of the leafspring I5 is exerted outwardly against the link I2 in one directiononly, the link I2 thus being held at-a slight angle with the inclinededge of the tongue II and thus maintained by means of the coil springI8, having a support rigid with the casing I. The hinged assemblies makepossible an increased sensitivity of operating pressure. a

As illustrated by the Figure 1, the oscillating body member I andconnected parts of the precision switch mechanism are held at-rest in anover-centered position by means of said coil springs I8. In the Figure2, the mechanized parts are illustrated as having been operated by meansof manual pressure by the thumb I9 placed upon the push element 20whereby the link I2, together with the tongue II at the point'of theirhinged connection, is depressed against the tension of the coil springI8, thereby operating the tongue II from its over-centered positionrelative to the oscillating body member 'I to an under-centeredposition.

Due to the over-all length of the combined tongue II, link I2 andconnected leaf spring I5, within their operating open space IA, beingslightly greater than the entire opening IA, the tongue II, depressed bypressure upon the link I2 hinged therewith is forced to a relativelyflexed condition with regard to the oscillating body member I. In suchforced movement from the over-centered position, through a center to anunder-centered position of the tongue II and link I! at their point ofhinged connection, the body member I is sufiiciently distorted so thatthe transition is one of sudden snap action wherein the free end of theoscillating body member I, carrying the superposed contacts 9 and I0,engages its contact 9 with the fixed contact 5, rigid with the casing I,which contact engagement is maintained against the tension of the coilspring I8 as long as manual pressure remains upon the push element 20,as illustrated by the Figures 2and 7. With the release of such mam ualpressure, the coil spring I8 acts to reverse the operation of themechanical parts with the same sudden snap-action as when manually operated. Insuch reversal of action however the tongue II at the hingedconnection of the link I2 passes back through center to its her llymaintained over-centered position, agai turning the engagement of theCOI'ltflCtjlUWlIiljl the fixed contact Ii rigid with the casirigfI/ajsillustrated by the Figures 1 and 6, the engagement being augmented bymeans of the coil spring i8.

While manual pressure is herein illustrated as means by which theprecision switch is operated to one of itsextreme positions, it is to beunderstood that such'movement of operation is adapted to be accomplishedby any other means, such as when the invention is employed as a part ofan automatic means adapted for precision con' trol in mass production ofan article, in which case the switch may be mechanically operated as apart of such means.

In the Figures 6 and '7, it will be noted that the full line Idesignates the body of the oscillating member, and the dotted line i irepresents the tongue member. In the Figure 6 the tongue ii, at its endconnected with the link 12, is shown over-centered with relation to thebody of, the oscillating member 1 while, in the Figure '7 the tongue I!at said end is shown under-centered with relation to said body i, suchpositions of the tongue H determine engagements of the contacts 9 and Icarried by the body member 1 relative to the fixed contacts and 5.

The novel introduction herein of the hinged link 12 as an extension ofthe tongue H, makes it possible to build said switch mechanism within ashort and more compact casing; for a length of a tongue equal to thecombined short length of the tongue H and link l2 would tend to addstifiness and thus increase the required exertive pressure of operation.The hinged assembly, as employed by said mechanism, allows a. greaterdifierential movement as between the push element and the travel of theoscillating member 7 between the fixed contacts 5 and 6.

I claim:

l. A snap-acting control mechanism for a precision switch comprising anoscillating body member having one end fixed to a supporting base andcarrying at the free end contact surfaces for alternate engagements withrelatively fixed contacts rigid with said base, said body member havinga central elongated opening therethrough; a tongue secured at one end tosaid body member within said opening; a leaf spring supported'by saidbase within said opening adjacent the free end of said tongue andexerting its tension outwardly along the plane of said opening; a linkmember interposed between said spring .and said tongue; a hingedconnection between said leaf spring and said link and between the linkand the free extremity of said tongue, the connected tongue, link andspring requiring a length of space greater than that of said opening,the said tongue is normally flexed to an over-centering position withrespect to said body member thus distorted and engaging one of itscontact surfaces with one of the fixed contacts; operating means to movesaid link, and

' hence the free end of said tongue with a snapaction from saidover-centering position, through a-center and to an under-centeringposition to release said contact engagement and to engage the othercontact surface with the other of said fixed contacts; and means foreffecting the return movement of the oscillating member.

' and. A snap-acting control mechanism for a precision switch comprisingan oscillating body member having one end fixed to a supporting base-andcarrying at the free end contact surfacessfor, alternate engagementswith relatively fixed :contactsrigid with said base, said body memberhaving. a central elongated opening therethrough; a tongue secured atone end to said body member within said opening; a leaf spring supportedby said base within said opening remote from said contact surfaces andexerting its tension outwardly along the plane of said opening; a linkmember within said opening and having hinged connections with the freeend of said tongue and with said leaf spring, the connected tongue, linkand spring requiring a length of space greater than that of saidopening, the said tongue is normally flexed to an over-centeringposition with respect to said body .member thus distorted and engagingone of its contact surfaces with one of the fixed contacts; manual meansfor operating said link, and hence said connected tongue with asnap-acting movement from said over-centering position, through a centerand to an under-centering position to release said contact engagementand engage the other contact surface with the other of said fixedcontacts; and separate spring means to effect the return movement of theoscillating member.

3. An oscillating member for a snap-acting control of a precisionswitch, said member comprising a sheet-metal body of which one end issecured to a base and the opposite end is provided with contactsurfaces, said body having an elongated opening therethrough; a tonguewithin a portion of said opening and secured at one end of said body; aspring supported by said base within said opening remote from saidcontact surfaces; a link member interposed between the free end of saidtongue and said spring; and hinged connections of said tongue, link andspring in such manner that their overall length is greater than that ofsaid opening.

4. An oscillating member for a snap-acting control of a precisionswitch, said member comprising a sheet-metal body of which one end issecured to a base and the opposite end is provided with contactsurfaces, said body having an elongated opening therethrough; a tonguewithin a portion of said opening and secured at one end of said body; aleaf spring supported by said base within said opening remote from saidcontact surfaces and exerting a tension in one direction; a link memberinterposed between the free end of said tongue and said spring; and ahinged connectionof said tongue, link and spring in such manner thattheir overall length is greater than that of said opening.

5. An oscillating member for a snap-actingcontrol mechanism for aprecision switch, said member comprising a sheet-metal body of whichsecured at one end to said body member; a spring supported by said baseremote from said contact surfaces;a link interposed between said tongueand said spring; and a hinged connection of said link with said springand the free end of said tongue, the overall length of the connectedtongue, link and spring being greater than the space between the placeof securement of said tongue to said body member and the supporting baseof said spring.

EDWIN AUGUST MILLER.

REFERENCES CITED UNITED STATES PATENTS Name Date Wilms Oct. 28, 1941Number

